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Dawn approaches Ceres, From opnav images to first orbit
Habukaz
post Feb 25 2015, 02:57 PM
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RC2 images are now out on the Photojournal: http://photojournal.jpl.nasa.gov/keywords/dp


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Explorer1
post Feb 25 2015, 03:07 PM
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Wow! Some big basins. Almost like the flats on Triton, though it must only be a skin-deep resemblance....

Worth the wait!
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TheAnt
post Feb 25 2015, 03:09 PM
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Max Planck Institute have now added a press release with new images.

Two glimpses of dwarf planet Ceres.
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Habukaz
post Feb 25 2015, 03:22 PM
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QUOTE
"Ceres' bright spot can now be seen to have a companion of lesser brightness, but apparently in the same basin. This may be pointing to a volcano-like origin of the spots, but we will have to wait for better resolution before we can make such geologic interpretations," said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.


http://dawn.jpl.nasa.gov/feature_stories/B...r_Companion.asp

Oooh blink.gif


I like the sound of that.

And also still too small to resolve:

QUOTE
"The brightest spot continues to be too small to resolve with our camera, but despite its size it is brighter than anything else on Ceres. This is truly unexpected and still a mystery to us," said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research, Gottingen, Germany.


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Explorer1
post Feb 25 2015, 03:29 PM
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The final albedo must get higher and higher as the predicted size of the spots drops, right? Things are getting very intriguing....
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volcanopele
post Feb 25 2015, 03:48 PM
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Here are Celestia previews of those two frames, just to give a sense of the geometry:
Attached Image

Attached Image


To be honest, I'm now more interested in this impact basin. Looks fresh, but it has very muted topography. Maybe it was big enough to reach a liquid layer beneath the crust.


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MarcF
post Feb 25 2015, 03:56 PM
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As I expected a Mimas-like surface I'm really surprised to see that some regions are far from being saturated with craters. And these bright spots... This dwarf planet gets really interesting !
Can't wait to see more next Monday, during the NASA briefing !!
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Phil Stooke
post Feb 25 2015, 04:20 PM
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There seems to be a rush to claim the big basin as young. That's not correct. Look at the craters inside it - at least the spatial density of larger craters in Mare Imbrium. The basin is old, it's erased a background of large craters and is filled with plains, but since then lots of mid-sized craters have formed. This is quite similar to lunar crater distributions (in general terms) so the chronology can't be very different.

Phil



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vikingmars
post Feb 25 2015, 04:39 PM
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QUOTE (Phil Stooke @ Feb 25 2015, 05:20 PM) *
There seems to be a rush to claim the big basin as young. That's not correct. Look at the craters inside it - at least the spatial density of larger craters in Mare Imbrium. The basin is old, it's erased a background of large craters and is filled with plains, but since then lots of mid-sized craters have formed. This is quite similar to lunar crater distributions (in general terms) so the chronology can't be very different.
Phil

100% agree with you Phil !
I think that some experts like Hartmann, Neukum, Salamunićcar, Barlow, etc... are excited to see the next images that will be taken at higher resolution to refine their size-frequency distribution (SFD) of impact craters. No doubt that Ceres seems to be one of the perfect planetary bodies (not too big and not too small) to calibrate crater-SFDs smile.gif
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Bjorn Jonsson
post Feb 25 2015, 04:41 PM
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It's a bit surprising to me how shallow the big crater/basin seems to be. Also it now seems very unlikely that Ceres has anything resembling Tethys' Ithaca Chasma (there were some speculations on that here earlier on). It probably was simply an albedo feature plus shadows within crates in the earlier, lower resolution images.

The bright spots are interesting. To me they simply look like fresh ice that has been exposed by impacts but apparently they might be something else.
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volcanopele
post Feb 25 2015, 04:41 PM
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True, young and fresh certainly are relative terms...

QUOTE (Bjorn Jonsson @ Feb 25 2015, 09:41 AM) *
The bright spots are interesting. To me they simply look like fresh ice that has been exposed by impacts but apparently they might be something else.

Most still look like fresh ice exposed by recent impact, just by small impacts. The one that kind of looked like a five-legged creature in last week's view now looks like a lot like the ray crater in Anguta, Rhea.


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elakdawalla
post Feb 25 2015, 04:43 PM
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There's a new Dawn Journal with an updated table.
QUOTE (John Broughton @ Feb 24 2015, 09:14 PM) *
Most here will be well aware of Marc's last blog post. Note that OpNav 3 took place a day later than listed there. I'm not after approximate figures - there'd be no point. If I could get distances at two times around Feb 4.4, I could extrapolate them for individual images within 100km and make some measurements; to clear up a discrepancy between the diameter measured by HST and a well-observed occultation -- or we could wait who knows how long for official figures. I already have a figure for the sidereal rotation period over an eleven-year interval!

Keep in mind that the RCs and OpNavs follow some or all of Ceres' 9-hour rotation, so they can, of course, begin on one day and end on another, and a photo release could come from either day.


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DFortes
post Feb 25 2015, 04:45 PM
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QUOTE (vikingmars @ Feb 25 2015, 04:39 PM) *
I think that some experts like Hartmann, Neukum, Salamunićcar, Barlow, etc...


Gerhard Neukum passed away last year, but is no doubt as excited as the rest of us on whatever astral plane he now inhabits.
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Habukaz
post Feb 25 2015, 05:14 PM
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QUOTE (Bjorn Jonsson @ Feb 25 2015, 05:41 PM) *
It's a bit surprising to me how shallow the big crater/basin seems to be. Also it now seems very unlikely that Ceres has anything resembling Tethys' Ithaca Chasma (there were some speculations on that here earlier on). It probably was simply an albedo feature plus shadows within crates in the earlier, lower resolution images.


Isn't the easternmost ("rightmost" in the the earliest OpNav images) part of those apparent linear features the apparently relatively smooth terrain seen in the right frame in today's release?:



(south should be to the bottom; image rotated 90 degrees clockwise from the original)

Not particularly valley-like (and not particularly un-valley-like, either), but to me it looks like it could still be a real thing. It looks considerably smoother than the terrain at the same latitude to the east in the same frame.

In the absence of the full rotation sequence, it seems hard to judge whether it's a real feature or not.


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Bjorn Jonsson
post Feb 25 2015, 05:23 PM
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QUOTE (Habukaz @ Feb 25 2015, 05:14 PM) *
Not particularly valley-like (and not particularly un-valley-like, either), but to me it looks like it could still be a real thing. It looks considerably smoother than the terrain at the same latitude to the east in the same frame. In the absence of the full rotation sequence, it seems hard to judge whether it's a real feature or not.

There might be a gentle dpression there but if so it's not nearly as clearly defined as Ithaca Chasma.
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